A common method for manufacturing spark plugs involves assembling a center electrode assembly into an insulator and then mounting the insulator in a tubular shell to which a ground electrode was previously attached. The projecting spark gap tip of the center electrode is trimmed to project to a predetermined location relative to the adjacent end of the spark plug shell and the ground electrode is bent to form a predetermined spark gap. It is necessary to trim the projecting center electrode tip to compensate for tolerance variations in the insulator, the center electrode, the shell and the assembly of these components. There are several disadvantages to trimming the center electrode tip. The exposed tip of the center electrode typically is made from an expensive corrosion resistant metal such as a nickel alloy. Trimming the electrode tip results in a waste of expensive material. If the trimming equipment is not properly adjusted, trimming the tip of the center electrode after it is mounted in the insulator may apply undesirable stresses to the insulator which sometimes can crack the insulator. Trimming also requires equipment and labor which add to the manufacturing costs for the spark plug.